I wrote in an earlier post about the two ex-Marines riding WorkCycles Secret Service bikes around the world. They previously sent a photo anonymously from their Blackberry (that much I could read in the email) of one of them somewhere in the UK. Well now they’re apparently somewhere else, judging from the different, hilly scenery in this photo. And they’ve traded camera duty thus we see our other protagonist in this story… though I honestly can’t remember which one of the two is Sage. I think it’s the guy in this picture. Detailed descriptions are clearly not their forte.
[UPDATE: In this photo we see Cooper while in the previous photo it's Sage. Glad that's cleared up.]
Speaking of riding the Secret Service in terrain hillier than pannekoeken flat Holland and also of non-detailed descriptions, we were tinkering with Shimano roller brakes today. Shimano makes several versions of their nearly maintenance-free roller brake but their literature and website offer almost no information about the differences between them. Countless conversations with the Shimano tech support guys were fruitless. There are three basic versions of roller brakes commonly found on quality bikes:
For about a year or so we’ve been fitting the IM70 to all Bakfiets Cargobikes and the Secret Service, partially because they look cool but mostly because it clearly has a more consistent, snappy feel and is more powerful. This baffled us since the braking unit in the center of each rollerbrake seemed to be exactly the same unit. In theory then there shouldn’t be much difference.
But today our chief mechanic Eric showed me something new: They’d opened up one of each type of rollerbrake to check out the guts and it turns out that the IM70 is actually special. While the IM40 and IM50 share the same flat braking surface (like a drum brake except in steel), the IM70 has a “V” shaped, or rather double conical braking surface. This gives it more braking surface area and probably makes it self-adjusting as well.
The problem though is that the front IM70 doesn’t have it’s own cable stop, thus meaning that it only fits on front forks equipped with a little cable stop tab. Many bikes don’t have these.
Enter the Shimano IM80 roller brake due for introduction shortly. Again the Shimano literature is just worthless marketing garble but at least it’s visible from the photos that the cable stop is built into this one. Let’s just hope that they’re using the better V-shaped brake surface.
Oh, just to back up a little here… “What’s a roller brake” you might ask, or perhaps a little more advanced question: “how is a roller brake different from a drum brake or a disk brake?” I’ll try to explain briefly, without photos. If that doesn’t work I’ll try again later WITH photos.
Drum brake: Two semi-cylindrical “shoes” get pressed against the inside of a cylindrical drum. The drum rotates with the wheel while the shoes are stationary in the frame or fork. The shoes are pressed outward at one end by means of a cam. More sophisticated drum brakes have been fitted to motorcycles and cars but, to my knowledge, never to bicycles.
Disk brake: A disk rotates with the wheel and the sides of the disk get squeezed by flat pads. The pads can be either cable actuated through a helix or hydraulically actuated.
Roller brake: The IM40 and IM50 are basically just drum brakes with a six lobed actuation cam that presses the shoes outward radially over their whole length instead of just at one point. The roller brake shoes are also steel, running in a bath of special graphite grease. Does your rollerbrake make noise? Squirt fresh grease in.
The IM70 roller brake has the same actuation as the IM40 and IM50 but uses a special type of drum described above.
I’m sure that’s all just totally clear for you know.